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A176304
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a(n) = (-1)^n * n * a(n-1) - 1, with a(0)=0.
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3
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0, -1, -3, 8, 31, -156, -937, 6558, 52463, -472168, -4721681, 51938490, 623261879, -8102404428, -113433661993, 1701504929894, 27224078878303, -462809340931152, -8330568136760737, 158280794598454002
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OFFSET
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0,3
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COMMENTS
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The sequence alternates in the sign and in the odd-even parity.
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LINKS
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MAPLE
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a(n):=`if`(n=0, 0, (-1)^n*n*a(n-1) -1); seq(a(n), n=0..20); # G. C. Greubel, Nov 26 2019
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MATHEMATICA
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a[n_]:= a[n] = If[n==0, 0, (-1)^n*n*a[n-1] -1]; Table[a[n], {n, 0, 20}]
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PROG
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(PARI) a(n) = if(n==0, 0, (-1)^n*n*a(n-1) -1); \\ G. C. Greubel, Nov 26 2019
(Magma)
function a(n)
if n eq 0 then return 0;
else return (-1)^n*n*a(n-1) -1;
end if; return a; end function;
(Sage)
@CachedFunction
def a(n):
if (n==0): return 0
else: return (-1)^n*n*a(n-1) -1
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CROSSREFS
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KEYWORD
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sign,easy
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AUTHOR
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STATUS
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approved
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